The present invention relates to taut band or filament-suspended rotors and stators used in meters.
Analog meters for measuring electrical quantities of the permanent magnet moving coil type include both the suspension galvanometer and the very popular D'Arsonval mechanism. Each of these movements broadly includes two major functional assemblies--the rotor and the stator. The rotor includes a coil of fine wire, and the stator includes the magnet and scale; a suspension system mechanically joins the rotor and stator. Of the various suspensions that have been used for permanent magnet moving coil mechanisms, one type involves a pair of fine filaments suspending the coil and is used principally in suspension galvanometers. A similar suspension uses taut bands, which are short metal-alloy ribbons or bands under tension. A further type is the pivot and jewel mechanism, which uses a jeweled bearing similar to those used in clocks and watches. The present invention relates particularly to the filar and taut band suspensions. As used herein, the term "filar" is meant to refer to both the fine filament and the taut band types.
In prior art the filar suspended rotor has always been assembled as part of a complete instrument. Individual rotor parts were mounted or secured in or around the stator parts, which included the spring components to provide tension to the suspension system. This practice has at least two disadvantages. First, the delicate rotor parts must be handled together with the larger and more massive stator parts, thereby exposing the rotor to potential damage. Second, the rotor has limited accessability when mounted in the stator.
Accordingly, the principal object of this invention is to provide a new design for a rotor for a D'Arsonval or electrodynamometer electrical instrument to overcome these problems inherent in the prior art.
Another main object is to provide a rotor which may be completely assembled and balanced as an independent unit and later placed in a suitably adaped stator.
A further object of the present invention is to provide such an improved rotor which includes structure to limit the axial and lateral movement of the filament or taut band. Such structure is desirable since it allows the meter to be used in a more rugged environment and retain substantially its accuracy despite being jolted, banged or dropped. An example of such structure is disclosed in my U.S. Pat. No. 3,678,383, entitled "High Impact Withstanding Taut Band Suspension Instrument."